Uriel Angulo-Zamudio, Mexico

Autonomous University of Sinaloa Faculty of Chemical Sciences Biological

Author Of 2 Presentations

STREPTOCOCCUS PNEUMONIAE GENERATES HYDROXYL RADICALS TO RAPIDLY INTOXICATE AND KILL STAPHYLOCOCCUS AUREUS STRAINS (ID 256)

Abstract

Background

Streptococcus pneumoniae (Spn) strains rapidly kills Staphylococcus aureus (Sau) by producing membrane-permeable hydrogen peroxide (H2O2). The exact mechanism by which the H2O2-mediated killing occurs is not well understood.

Methods

An in vitro model that mimicked Spn-Sau contact during colonization of the upper airways and whole genome sequencing was conducted. Different Spn H2O2 mutants were constructed to confirm the Sau killing mechanism.

Results

Sau killing required outcompeting densities of Spn. A collection of MRSA/MSSA strains showed a linear sensitivity (R2=0.95) for Spn killing but the same strains had different susceptibilities when challenged against pure H2O2. WGS of these MRSA/MSSA strains revealed no association between clonal complex and susceptibility, or resistance, to Spn, or H2O2,respectively. A sublethal dose (~1 mM) of pure H2O2 when incubated with TIGR4DspxB eradicated cultures of Sau strains suggesting that Spn converts H2O2 to the hydroxyl radical (·OH). Accordingly, Sau killing was completely blocked by incubating with scavengers of ·OH radicals, DMSO, or thiourea.

Conclusions

Spn produces H2O2 which is rapidly converted to a more potent oxidant, the ·OH radical. Hydroxyl radicals does not affect Spn viability but rapidly intoxicate Sau strains. The target(s) of the ·OH radicals represents an exciting new alternative for the development of therapeutics against Sau infections.

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TARGETING ERADICATION OF PNEUMOCOCCAL CARRIAGE WITH FDA-APPROVED DEOXYCHOLIC ACID (ID 828)

Abstract

Background

Nearly 1 billion children worldwide carry Streptococcus pneumoniae (Spn) in the upper airways. Human bile salts are known to dissolve the Spn cell wall of which deoxycholic acid (DoC) is approved by the FDA for aesthetic treatment (10 mg/ml). We investigated the antimicrobial effect of DoC against pneumococcal strains.

Methods

Dose-response and time-course studies were conducted with Spn reference strains (N=2) and MDR strains (N=3). We then challenged Spn strains (N=55), including vaccine types, and other oral bacterial species (N=21) with a MIC90 and viability was investigated. An in-vitro model of pneumococcal colonization assessed the antimicrobial activity in a life-like scenario.

Results

MIC90 was achieved with 0.5 mg/ml of DoC incubated for 2 h with vaccine and non-vaccine type strains and reference strains TIGR4 and D39. The pneumococcal colonization model demonstrated that DoC eradicated 107 cfu/ml of MDR strains bearing resistance to Penicillin, Meropenem, and/or Erythromycin within 20 min post-exposure. Viability of most oral bacterial species was not affected by a treatment with a Spn-MIC90.

Conclusions

DoC eradicated Spn strains with a MIC90 20-fold lower than the recommended human dose. It has the potential for prophylactic eradication of Spn carriage from the upper airways with no disturbance of other oral bacteria.

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